It is a prevalent method in the turbine and pump industry that before the making of the 1:1 scale machine a smaller model is made, and the measurements performed on the model can be applied to the prototype because of the similarity. In case of successful measurements the production of the prototype can be started. During the turbine measurement, which is performed in a closed hydraulic system, a pump circulates the water in the system. The pressure difference caused by the pump provides the pressure head between the presser and the suction side of the turbine. An air cushion can be found in the measuring circuit equipped with an air-pump and a compressor to set the correct pressure difference in a given operating point, cause changing the pressure of the air cuscion occurs in all parts of the plant. Two types of measurements can be performed by the measuring circuit, effiniency measurement and cavitation measurement. To get satisfying results the measurement shuold be repeated in different guide vane and runner blade angle positions. Therefore the number of the carried out measurements can reach up to 1300 operating point which should be processed. A powerful variable speed motor (110 and 75 kVA) and a variable frequency drive is connected to both the pump and the turbine. With these you can control the operating point of the turbine. The volume flow rate of the pump can also be controlled. The purpose of the measurement is that the measured quantities in an operating point, which represented by the preset runner blade and guide vane angles, could be compared to the previous calculations. To calculate efficiency volume flow, pressure, torque, rotational speed and temperature measurements are required, control of the valve switching modules is also needed. Prior expectations set up against the system are reliability, interference immunity, and to be expandable. A display and control panel should be included. To maintain accuracy of 0,1% of the sensors in their whole measuring range is a special challenge. The main topic of my dissertation is to design a data acquisition modul, which is suitable for temperature, rotational speed, torque, volume flow and pressure sensors' signal reception and to control valves and variable frequency drives.
The modul should be able to measure the required quantities with the specified frequency, then store and forward them through an appropriate communication interface.